1. Field of the Invention
The present invention relates generally to carpentry tools and more particularly to an automatically retracting chalk line dispenser for conveniently dispensing and retracting a chalked string, such as those commonly used by carpenters to form straight lines.
2. Description of the Related Art
Chalk lines used by carpenters in the construction of buildings and the like are well known. Chalk lines are commonly used for marking structures, such as walls, floors, and ceilings, as well as the associated drywall or other paneling used in the construction thereof. The use of a chalk line provides the carpenter with a straight line along which another structure may be aligned or a cut may be made.
Contemporary chalk line dispensers typically comprise a housing in which a quantity of chalk dust may be disposed and inside of which a spool of string is pivotally mounted such that the string may be extended from the housing while carrying thereupon a small amount of chalk dust. The string is extended such that it coincides with a line for which marking is desired. The string is then held stationary at both ends and plucked near the middle such that chalk dust is shaken from the string when the string impacts the surface to be marked, thereby forming a straight line between the two ends of the string. A line catch or hook may be utilized to anchor the string at the distal terminus of the line to be formed while the chalk line device is held stationary at the lines proximal the terminus by the user. The string is typically manually retracted into the device via a rotatable handle and winding mechanism.
The use of such chalk line devices is common both because of the ease with which straight lines are formed therewith and because of the temporary nature of the lines so formed. A straight line may be formed in a matter of seconds by a single user. The chalk so disposed upon the surface to be marked can be easily brushed away after having served its intended purpose if so desired.
Various automatically retracting chalk line dispensers are known. Typical of such devices is that described in U. S. Pat. No. 4,813,145 issued to Josey Jr. et al. The Josey device comprises a housing in which a spool is disposed. A spring is disposed within the spool to provide for retraction of the string after use. A hub formed upon the spool extends through the housing such that rotation of the spool may be controlled. This provides the user with a means of reducing the speed with which the string retracts into the device. A locking device is incorporated into the hub to lock the spool in place after the string has been extended. In the locking mechanism of the Josey device, a leaf spring attached to the hub is tensioned against the housing to provide a frictional engagement thereto. As those skilled in the art will recognize, such a frictional locking mechanism is subject to slippage.
Slippage of the locking mechanism on such contemporary chalk line devices results in a hazardous situation wherein the line and line catch or hook are retracted uncontrollably toward the chalk line device and may thereby whip around and potentially inflict damage and/or injury. Thus, it would be desirable to provide a positive locking means which assures that the string and line catch or hook will not be inadvertently and uncontrollably withdrawn into the chalk line device.
Additionally, the intentional retraction of the string and line catch or hook into contemporary devices may result in an uncontrolled retraction in those instances where the speed of retraction is not dampened. In the JOSEY device such damping may be manually applied by squeezing the hub of the device to effect slowing of retraction. However, other contemporary devices lack this feature and are therefore subject to uncontrollable retraction even during the intentional actuation of the retraction mechanism. Thus, it would be desirable to provide a means for automatically limiting or damping the speed of the spool during the retraction process in order to prevent uncontrollable retraction of the string and line catch or hook in order to prevent potential damage and/or injury.
Furthermore, contemporary chalk line devices are susceptible to failure caused by jamming of the retraction mechanism resulting when an excessive quantity of chalk dust surrounds and adheres to the retraction mechanism. Attempts to seal the retraction mechanism from the chalk containing reservoir have been frustrated by manufacturing requirements dictating simplicity of design and ease of assembly to maintain low cost. For example, in the Josey device it is possible for chalk dust to migrate between the spool and housing and then through the spindle aperture to the inside of the spool where the spring is located. Entry of a sufficient quantity of chalk dust may thus foul operation of the spring and thereby reduce the reliability of the retraction mechanism.
Although acceptable for their intended purpose, contemporary chalk lines such as the Josey device generally lack a positive locking means, require that the user manually effect and/or slow retraction of the string, and are susceptible to jamming of the retraction mechanism by entry of chalk dust into the spool where the spring is disposed. As such, although the prior art has recognized to a limited extent the problem of providing an automatically retracting chalk line dispenser, the proposed solutions have to date been ineffective in providing a satisfactory remedy.